(1) Field of the Invention
This invention relates to a passive seat belt system for a vehicle, more specifically to a mechanism for the positional adjustment of an anchor for a webbing in a passive seat belt system, and especially to a mechanism for permitting adjustment of the height of a webbing anchor relative to the outboard shoulder of an occupant in a passive seat belt system for a vehicle.
(2) Description of the Related Art
A passive seat belt system for a vehicle serves to restrain and protect an occupant by fastening a webbing in the event of a vehicular emergency such as a collision. As illustrated in FIG. 10, the conventional passive seat belt system is designed to support the webbing by an anchor base provided adjacent the outboard shoulder of the occupant when the seat belt system is in use.
The sitting height and other physical constitution vary widely from one occupant to another, who use a seat belt system. It is therefore necessary from the viewpoint of safety to permit adjustment of the position of attachment of the anchor base which supports the shoulder webbing in the vicinity of the outboard shoulder of the occupant. If the anchor base for the shoulder webbing is positioned too high, the webbing extends over his face or neck. If it is positioned too low on the other hand, the webbing gets out from his outboard shoulder and extends over his outboard arm. Whichever the case may be, there is the potential danger that the webbing may not be able to protect the occupant effectively in the event of an emergency. To solve this problem, a mechanism is provided to permit adjustment of the position, typically, the height of the anchor base.
In such a conventional adjustment mechanism, an adjustment base which serves to transmit to a vehicle body a load applied to the anchor base in the event of a collision is mounted on a center pillar of the vehicle body. A slide rail and the anchor base are provided either forwardly or rearwardly of the adjustment base. This has made the adjustment mechanism wider and thicker. If the adjustment mechanism is designed to bear the load of a collision by the slide rail without using any adjustment base, it is necessary to thicken the aluminum material of the slide rail to enhance the strength of the slide rail. Moreover, it is also necessary to form, in the slide rail, plural holes for the positional adjustment of the anchor base. Such a design therefore requires complex machining steps.